1. Field of the Invention
The present invention relates to a gas turbine control method and the device thereof; thereby, the fuel flow rate or air flow rate to be supplied to combustors is increased and decreased in order to obtain operation condition under which no combustion vibration occurs.
2. Background of the Invention
In the conventional gas turbine plants, with respect to the parameters such as the power output of the generator and the ambient temperature, the flow rates of the fuel and the air supplied to the combustors are predetermined; the air flow rate or the air flow rate is fine adjusted in the test runs of the gas turbine. After being commissioned, the gas turbine is operated based on the fine adjusted fuel flow rate and airflow rate as established standard setting-values.
According to the control method as described above, however, there remains a possibility that the fuel contents, the fuel flow rate and the airflow rate in the practical operation deviate from those in the commissioning condition, as the components and calorific value of the fuel supplied to the gas turbine may change and the secular change such as the deterioration of the compressor performance or the filter clogging may happen.
Further, because of the deviation described above, there may be caused apprehension that the combustion stability may be hindered and combustion vibrations consequently occur, the operation of the gas turbine plant being seriously hampered. Hence, it is strongly requested to evade the occurrence of the combustion vibrations, in view of protection of the facilities in the plant as well as enhancement of the availability (the rate of operation) of the gas turbine.
The patent reference 1 (JP1993-187271) discloses a control method for controlling the gas turbine plant so as to maintain the stable combustion; thereby, the airflow rate or the fuel flow rate as to the gas turbine combustor is controlled in response to the change in the calorific value of the fuel based on the contents (components) in the fuel.
In the control method disclosed in the patent reference 1, the bias control regarding the airflow rate or the fuel flow rate is made use of; namely, the bias coefficient is established in response to the change in the calorific value of the fuel, based on the contents in the fuel; and, the change in the calorific value is multiplied by the bias coefficient to obtain a correction value that is added to or subtracted from the standard setting value regarding the fuel flow rate or the airflow rate; thus, the fuel flow rate or the air flow rate is adjusted.
However, according to the above-described method, the bias coefficient corresponding to the change in the fuel calorific value is uniquely established; thus, the degree of freedom as to the control adjustment is limited; and, it is difficult to adjust the airflow rate or the fuel flow rate so that each of the flow rates converges to an optimally controlled value.
To this end, the inventors of the present invention have proposed a gas turbine control device in the patent reference 2 (JP2006-183652), so as to improve the above-described problem. Firstly, the proposed control device is now explained with reference to FIGS. 4 and 5; the entire contents of the patent reference 2 (JP2006-183652) are hereby incorporated by reference.
In FIG. 4, the gas turbine plant 100 comprises the gas turbine 102 that is rotationally driven by the thermal energy produced by the combustion of the supplied fuel and the gas turbine control unit 104 that controls the gas turbine 102.
The gas turbine 102 is provided with: the process variable measurement device 106 that measures each process variable (the plant state variable) that indicates the operation condition or the operation state regarding the gas turbine 102; the pressure variation measurement device 108 and the acceleration measurement device 110 that are fitted to the combustors (described later in detail) 32 (cf. FIG. 1) installed in the gas turbine 102; the maneuvering mechanism 112 that manipulates each actuating part of the gas turbine 102. Incidentally, the process variables include, for instance, the flow rate as to the fuel and the air that are supplied to each combustor 32.
The gas turbine control unit 104 is provided with: the controller 114 that generates the control signals to be transmitted to the maneuvering mechanism 112 on the basis of the signals from the process variable measurement device 106, the pressure variation measurement device 108 and the acceleration measurement device 110; the automatic tuning section 120 that adjust the control signals generated by the controller 114.
In the next place, the configuration of the automatic tuning section 120 is now explained with reference to FIG. 5. As shown in FIG. 5, the automatic tuning section 120 comprises:
the input means 122 in which the process variable (e.g. the fuel flow rate or the airflow rate) as a measured result (value) at each part of the gas turbine 102 is inputted;
the frequency analyzing means 124 that analyzes the pressure fluctuations or the accelerations regarding each combustor 32 per each predetermined frequency bandwidth;
the operation status grasping means 126 that grasps the (operation) state of the gas turbine 102;
the combustion characteristic grasping means 128 that establishes mathematical formulae (models) which model combustion characteristics, on the basis of the process variables regarding the gas turbine 102 as well as on the basis of the combustion vibration analysis results per each predetermined frequency bandwidth, the analysis results being stored in the database (data table) provided in the combustion characteristic grasping means 126, for confirming the operation state of the gas turbine;
the countermeasure decision means 130 that establishes the adjustment (increment) regarding each (actuating) part of the gas turbine, on the basis of the established mathematical formulae (models);
the output means 132 that outputs the adjustments established in the countermeasure decision means 130 into the controller 114.
Further, the gas turbine 102 is provided with the fuel property measuring means 116 as a component of the process variable measurement device 106, the fuel property measuring means 116 being used for measuring the fuel contents of the fuel gas supplied to the combustors. For instance, the fuel property measuring means 116 is configured as a gas analyzer that measures the fuel contents of the fuel gas. In the fuel property measuring means 116, the volume ratios regarding a plurality of fuel gas components in the fuel are measured; from the obtained volume ratios, the fuel content analysis is performed or the calorific value of the fuel gas is calculated. The result as to the fuel content analysis or the fuel calorific value is outputted as the measuring result.
The signal corresponding to the measuring result outputted by the fuel property measuring means 116 is inputted into the operation status grasping means 126; the signals corresponding to the measuring results obtained by the process variable measurement device 106 other than obtained by the fuel property measuring means 116 are inputted into the input means 122. Further, the signals corresponding to the measuring results outputted by the pressure variation measurement device 108 and the acceleration measurement device 110 are also inputted into the input means 122.
The pressure variation measurement device 108 measures the pressure fluctuations in the multiple combustors 32, while the acceleration measurement device 110 measures the vibrations of the combustors as accelerations; thus, the combustion vibration of each combustor 32 is measured. The data regarding the pressure fluctuations (the pressure vibrations) as well as the accelerations (the acceleration vibrations) are transmitted to the frequency analyzing means 124 via the input means 122; in the frequency analyzing means 124, frequency analyses are performed. In performing the frequency analyses, the whole frequency range to be treated is divided into n frequency bandwidths in advance; in each frequency bandwidth, the strength (the level) of the vibration is analyzed; thus, the maximum value of the vibration strength regarding each bandwidth is sought, and the maximum value is inputted into the operation status grasping means 126.
The operation status grasping means 126 judges whether or not the combustion vibration level of each combustor has to be immediately restrained by performing control adjustments, on the basis of the data regarding the process variables transmitted from the input means 122, the information regarding the components or the calorific value of the fuel the information which is measured and obtained by the fuel property measuring means 116, and the data regarding the maximum vibration strength in relation to the combustion vibrations the data which is obtained by the frequency analyzing means 124. Further, when the operation status grasping means 126 recognizes an abnormal condition in a certain bandwidth, the change of the plant operation state such as the plant load demand or the suction air temperature, then the data regarding each process variable including the information regarding the maximum value of the vibration strength as well as the information regarding the components or the calorific value of the fuel are accumulated as logged data.
The logged data are transmitted to the combustion characteristic grasping means 128; in the grasping means 128, based on the logged data, the mathematical model for modeling the combustion characteristics is formulated. In other words, in the combustion characteristic grasping means 128, the maximum value regarding the strength of the pressure vibrations in each frequency bandwidth is expressed with respect to the process variables such as the components or the calorific value of the fuel, or the air flow rate, the process variables being treated as independent variables; for instance, by use of linear multiple regression approach, the maximum values are expressed (modeled) in a set of linear functions of the independent variables. In addition, in a case of the modeling by the linear multiple regression approach, the coefficients regarding the independent variables in the linear expressions are determined (solved), for example, by use of the method of least square.
Incidentally, the measurement information data in the a fuel property measuring means 116 as well as the information data accumulated in the operation status grasping means 126 is transmitted into the combustion characteristic grasping means 128.
According to the mathematical model, the countermeasure decision means 130 identifies at least one process variable that tends to cause combustion vibrations in each frequency bandwidth; further, the countermeasure decision means 130 establishes the relation between each process variable (chiefly the fuel flow rate or the airflow rate) and the degree (level) of combustion vibrations; by use of the established relations (e.g. equations) regarding multiple process variables, a feasible domain regarding the multiple process variables where combustion vibrations are prone (or less prone) to occur is demarcated, for example, by the aid of the approach as is used in the field of linear programming. Further, on the basis of the information as to the demarcated domain where combustion vibrations are prone (or less prone) to occur, the correction values are established in the countermeasure decision means 130; hereby, the correction values are in relation to each process variable (e.g. the fuel flow rate or the airflow rate) and the corresponding actuating variable for manipulating and controlling the gas turbine 102. The data regarding the established correction values are inputted into the controller 114 from the output means 132.
As described above, the gas turbine operation conditions under which the combustion vibrations are difficult to occur are determined; operating the gas turbine according to the operating conditions prevents the combustion vibrations from occurring.
However, even though the above-described control method disclosed in the patent reference 2 is performed, it is not so easy to control the gas turbine with a high degree of accuracy, as the operators expect it is easy to control the gas turbine; the reason is that the relationship between the conditions causing combustion vibrations and the fuel properties (such as the components or the calorific value of the fuel) can be regarded as a strong nonlinear relation, and the combustion vibrations severely fluctuate. Hence, according to the conventional way as described above, it is difficult to completely restrain the combustion vibrations.